Rob Kardashian runs into Kylie Jenner, Tyga during workout

LOS ANGELES, Aug. 25 (UPI) -- Rob Kardashian ran into half-sister Kylie Jenner and her beau Tyga during his workout Monday.

The 28-year-old reality star revealed he's back on a fitness routine by sharing a photo from the chance encounter on Instagram. "Spotted these fools on the morning workout," he captioned the snapshot.

Kardashian largely keeps out of the spotlight, and rarely shares photos or updates on social media. Khloe Kardashian admitted her brother is "not at his happiest place" in March, and confirmed he is still living with her in July.

The reality star has struggled with his weight in recent years, and simply declared, "Yes I'm fat now," in February. He seems to have stayed active this summer, and sister Kim Kardashian tweeted they went on "the hardest hike ever" earlier this month.

Rob Kardashian ran into Kylie Jenner (L) and Tyga during his workout Monday. Instagram/Rob Kardashian

Kardashian and his family came to fame on E! series Keeping Up with the Kardashians, which will return from mid-season break in the fall. Jenner celebrated her 18th birthday on Aug. 10, and received a Ferrari from Tyga at the party.